Aldehydes in wine

Cullere, L., Cacho, J., and Ferreira, V, (2007). An assessment of the role played by some oxidation-related aldehydes in wine aroma. /. Agric. Food Chem. 55, 876-881. 

Puech, J. L. (1987). Extraction of phenolic compounds from oak wood in model solutions and evolution of aromatic aldehydes in wines aged in oak barrels. Am. J. Enol. Vitic., 38, 236-238. 

Finally, formation of 0-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBOA) derivatives and analysis by GC-Mass Spectrometry (GC-MS) and GC-Electron-Capture Detection (GC-ECD) appears to be a promising technique, de Revel and Bertrand (42, 43) used PFBOA derivatization to analyze a number of saturated and unsaturated aldehydes in wines, however, high concentrations of acetaldehyde made accurate quantitation of the other aldehydes present in lower concentrations difficult, depending on the wine matrix the aldehydes were not always well separated from other chromatographic peaks pH conditions for the derivatization were not specified and removal of excess PFBOA by acidification caused the partial loss of some aldehydes. In addition, no specific information regarding derivatization efficiency and recovery, or absolute limits of detection and quantitation were reported by these authors. 

THE GC/PICI-MS/MS OF WOOD VOLATILE PHENOLS AND BENZENE ALDEHYDES IN WINE... 

Acids can be produced by the oxidation of aldehydes or primary alcohols. For example, the souring of wine results from the oxidation of the ethyl alcohol in wine to acetic acid ... 

Panossian A, Mamikonyan G, Torosyan M, Gabrielyan E and Mkhitaryan S. 2001. Analysis of aromatic aldehydes in brandy and wine by high-performance capillary electrophoresis. Anal Chem 73(17) 4379-4383. 

AcetaJdehyde is old. It is not ancient like ethyl alcohol, the essential ingredient in wine, but it owes its discovery to this closely related compound. Scheele first prepared acetaldehyde in 1774 by dehydrogenation of ethyl alcohol. Just as many nicknames get attached to people at infancy, this process generated the name aldehyde. It is a contraction for compounds that are alcohol dehydrogenates. 

The dictionary (at least one late edition) says that an oenophile oeno-, wine philos, love) is a wine aficionado. And wine that has some aldehydes in it that never converted to ethyl alcohol is bad wine. 

Finally, reactions of flavonoid and nonflavonoid precursors are affected by other parameters like pH, temperature, presence of metal catalysts, etc. In particular, pH values determine the relative nucleophilic and electrophilic characters of both anthocyanins and flavanols. Studies performed in model solutions showed that acetaldehyde-mediated condensation is faster at pH 2.2 than at pH 4 and limited by the rate of aldehyde protonation. The formation of flavanol-anthocyanin adducts was also limited by the rate of proanthocyanidin cleavage, which was shown to take place at pH 3.2, but not at pH 3.8. Nucleophilic addition of anthocyanins was faster at pH 3.4 than at pH 1.7, but still took place at pH values much lower than those encountered in wine, as evidenced by the formation of anthocyanin-caffeoyltartaric acid adducts, methylmethine anthocyanin-flavanol adducts,and flavanol-anthocyanin adducts. The formation of pyranoanthocyanins requiring the flavylium cation was faster under more acidic conditions, as expected, but took place in the whole wine pH range. Thus, the availability of either the flavylium or the hemiketal form does not seem to limit any of the anthocyanin reactions. 

Similarly, catechin polymers formed upon horseradish peroxidase-catalyzed oxidation of catechin or polycondensation of catechin with aldehydes prove much more efficient than catechin (at identical monomer concentration) at inhibiting XO and superoxide formation. A more detailed investigation with the catechin-acetaldehyde polycondensate (which is expected to form in wine because of the microbial oxidation of ethanol to acetaldehyde) shows that inhibition is noncompetitive to xanthine and likely occurs via binding to the FAD or Fe/S redox centers involved in electron transfers from the reduced molybdenum center to dioxygen with simultaneous production of superoxide. 

Sulfur Dioxide. The legal limits for total sulfur dioxide in wines varies from 200 to 350 mg/liter. In addition, the limit for sulfur dioxide not bound to aldehydes, polyphenolic compounds, etc. may be from 30 to 100 mg/liter. Winery control requires that the amount of sulfur dioxide present during processing and aging be carefully controlled, and increasing concerns for public health reinforce this. 

Sulfur Dioxide and Aldehydes. Sulfur dioxide is commonly added both before and after fermentation in preparing white table wines. It is an effective antioxidant as well as a selective inhibitor of unwanted microorganisms. However, sulfur dioxide, as the bisulfite ion in solution, combines with aldehydes, especially acetaldehyde, during fermentation giving an accumulation of aldehydes in the bound form of aldehyde-sulfurous acid. 

In later investigations, Galetto et al. (IS) found eight strongly flavored acetals in wines from submerged flor culture. They suggest that the acetal to aldehyde ratio as a criterion of quality should be modified to reflect the species as well as the concentration of the acetal. 

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